How to test imagebuilder

## 💬 Questions and Help

I need to test imageBuilder, I have this code, but I can't.

```dart
testWidgets('Cached networked image builder', (tester) async {
final widget = CachedNetworkImage(
cacheManager: cacheManager, //<<< FakeCacheManager
imageBuilder: (
context,
url,
) =>
Container(
key: Key('image'),
),
progressIndicatorBuilder: (context, url, progress) => Container(
key: Key('progress'),
),
errorWidget: (context, url, error) => Container(
key: Key('failed'),
),
imageUrl: 'foo.nl',
);
await tester.pumpWidget(
MediaQuery(
data: MediaQueryData(),
child: MaterialApp(
home: widget,
),
),
);

await tester.pumpAndSettle();

expect(find.byKey(Key('image')), findsOneWidget);
});